bug#39662: 28.0.50; Emacs crashes in x_cr_define_fringe_bitmap if (fringe-mode 0)

[Robert Pluim]

>>>>> On Tue, 18 Feb 2020 17:54:05 +0100, Thibault Polge <thibault@thb.lt> said:

    Thibault> Thanks for the quick response!
    >> Perhaps we should signal an error for this case and have diff-hl deal
    >> with the fallout?

    Thibault> IMHO the issue is at least partially with emacs, not diff-hl (I 
just
    Thibault> didn't have time to dig further), so signaling seems more 
reasonable
    Thibault> than postponing the crash.

I took another look, signaling is not necessary, we can just make
define-fringe-bitmap set the width to 1 or some other reasonable value
if zero is passed in. Iʼd offer a patch, but Iʼm going to be busy for
the next week or so, so I can get to this afterwards.

    Thibault> (Also I should have specified that this may be a regression: I 
cannot
    Thibault> reproduce in 26.3.)

I haven't tried it in emacs-27, but it probably crashes the same way
there.

Robert